Process of making clad tubular articles.



W. M. PAGE.

PROCESS OF MAKING GLAD TUBULAR'ARTIGLBS.

APIL'IGA TION TILED APR. 20, 1910.

Patented Jan. 19, 1915.

. Articles, of which the following is a specifi- UNI ED STATES PATENT OFFICE.

WILLIAM IIAJasHALL PAGE, or PHILADELPHIA, rnNNsnva'N'm.

I PROCESS OF MAKING GLAD TUBULAR ARTICLES. I

cation.

This invention relates to processes of making clad tubular articles; and it comprises a method wherein a hollow or tubular body of ferrous or like metal is heated from one side to a suitable temperature and while so heated is united to a body of copper orlike metal; all as more fully hereinafter set forth and as claimed.

For= heat-exchanging elements, such as boiler tubes, and for many other purposes, the value of copper-clad steel is evident. In a boiler tube, for example, the strength of steel and the heat-conductive and corrosion resisting properties of copper are desirable. Steel corrodes and oxidizes easily and is relatively a poor conductor for' heat. In a boiler tube there is little lateral conduction of heat though this would. obviously be advantageous as equalizing the temperatures and diminishing the tendency of scale to bake on. Most of the heat from impinging flame gases is localized, little spreading laterallyfrom each point of impingement, so that part of the tube is not actively functioning while the residue is pushed to un due duty. As the amount of heat transmitted through a metal wall in a time .unit is a' compound function of the relative conductivity of the metal and the difference in temerature between the two sides, or heat hea this means that the high temperature gases first impinging do not transmit as much. heat in the time afforded as they should while being cooled somewhat on Speciflcation of Letters Patent.

Application filed April 20,

I Patented J an. 19, 1915. 1910. Serial No. 556,602.

mission of heat at the point where the furnace gases strike the boiler tube but also the zone of active heat transmission isbroadened out laterally. More of the tube is actively functioning. Copper is also highly resistant to corrosion, either ,by boiler waters or by furnace gases. But copper is a comparatively weak,'soft metal.

It is not desirable-to make a mere assemblage of concentric tubes of the two metals for boilers, partly because their expansion andcontraction are so widely different and partly because the line of non-union or seam between such tubes would tend to prevent eflicient transmission of heat. For quick transmission of heat, the two metals must be in metallic contact. In such an assemblage, furthermore, both metals must be present in suflicient thickness to give each layer of metal substantial strength of its own. Ordinarily copper-plating by electrolytic methods does not. give an eflicient article for this purpose, electro'deposited coatings being invariably porous, crystalline, and of little real adherence to their base, from which they tendto part on heating. Copper and steel forming an excel; lent galvanic couple, the presence of the porous copper tends to aid corrosion. For purposes like the present, the two metals must be in an absolute metallic union which is, or is equivalentto, a weld union so that they may not shrink apart and that they may transmit heat efliciently while the copper must be wholly impervious so that corrosive agents cannot reach the steel.

Joined copper and steel united by a union of this character have long been desired in the art; but until recently have not been produced. Copper and steel are so unlike in chemical and physical nature that they cannot be united by simple heat and pres- ,.sure 'in the way in which iron can be united t iron or even copper to copper. duce a firm union between metals they must be in acontapt which is, or is equivalent to, a molecular contact and to secure, this one or both the metals must be in a molten or at least fluent condition so that a liquid contact, or. wetting contact, can be secured. 9 to secure between steel and copper.

To pro-- such an intimate contact is not easily.

In the elder art, most of the attempts to weld-unite copper and steel failed from a lack of recognition of this fact. Hot-rolling the two metals together was often tried but gave at most a mere fitting together. or adhesion in lieu of a cohesion, never producing inseparably united metals, and the many attempts at casting the two metals together fared no better. In casting copper against steel under ordinary casting conditions for example, it is probable that no real metallic contact of the nature of a wetting contact ever resulted; partly, probably, because copper has little chemical or physical affinity for steel and does not readily wet If the steel body were hot it was usually oxidized on the surface with the oxid forming a physical spacing layer which prevented the liquid copper coming into actual contact with the steel while as the cast liquid copper solidified in the mold the gases evolved in solidifying went to the center; to the line between the hot steel core and the still molten parts of the copper. If the steel were clean and cold, the copper east against its surface solidified there before time was afforded for any actual contact or even for displacement of absorbed gases. Of late however it has been possible to attain true weld unions as by the methods described in Patent 853,716 where the copper is contacted with the steel in a superheated or supermolten condition; under which circumstances it readily wets and unites with it, forming unions which are, or are in the nature of, true weld unions. After cooling, good welds so efiected are inseparable save by heat sufficient to melt ofi the copper, a cleaving tool, such as cold chisel, or heating and quenching, failing to discover any line or seam of non-union and the joined metals may be rolled, drawn, swaged, spun and otherwise worked like a body of a single metal. It is however diflicult and expensive to roll or manufacture tubing and tubular articles directly from non-tubular shapes of clad metals; and there is a difiiculty peculiar to clad metal in forming such articles from tubularly bent sheets in that a double union must be formed at the seam to attain full strength. The operation isnot so simple as forming hollow articles-from steel or iron sheets or bars. in the present invention however I have devised a simple, cheap and ready method of directly forming steel or iron tubing and hollow articles clad with a coating of integrally and metallically united copper, or metal comprising copper, and with a union therebetween which is, or is equivalent to, a weld union. For this purpose I first prepare a steel or iron tube or hollow article of-nearly the final dimensions 4 required and then expose it to heat from one side while another side is in contact with a body of copper until the proper thermal and other conditions requisite for union between steel and copper are produced on the side of the steel in contact with said copper. Or, in

other words, I heat through the ferrous metal wall until proper heat and other conditions occur on the other side to produce the desired union between the ferrous metal and a proximate layer of molten cop- The heating may be by any convenient method or apparatus using fire or flame heat, electrical heating or even the heat of solid fuel. An oil or gas flame is, however, well adapted for use for the present purposes, such flame being, for instance, directed through or into the tubular or hollow body, or around it when the interior is to be clad.

The article may be either interiorly or exteriorly clad with copper. The copper may be brought into contact with the ferrous metal article to be clad or coated in any conexterior coating, copper wire may be wound around the article; or a suitable surrounding mold casing may be filled with chips, or other forms of finely divided copper. The article may receive a preliminary copper coating electrically. The coating metal in lieu of being pure copper may be any cupriferous alloy, such as brass. Brass while readily attached to'steel by the methods of Patent 853,716, is not readily rolled and otherwise worked at steel working temperatures, but as in the present invention no extensive subsequent working is necessary, the present method gives a convenient method of making brass clad tubular articles. Aluminum bronze and other bronzes may 'e used. A good coating material for many purposes is what may be termed an iron bronze; an alloy of copper and iron. While copper and iron stand far apart in the electrical scale so that copper promotes the corrosion of steel yet various of the iron bronzes are electrically neutral to iron and steel, be ing neither substantially positive or negative thereto, While they are, like copper, very resistant to corrosion. If desired, a layer of linking low melting metal may be used to facilitate the union, the steel article being, for example, first galvanized, tinned or sherardized.

blocking out mold of appropriate form may 'be employed to constitute with the interior of the article an annular mold. The steel or iron article to be clad or coated may first be sandblasted, pickled and cleansed, or it may be left covered with furnace scale; which consists mainly of ferrosoferric oxid and may have a useful function in the union,

body like waterglass or borax or one of the halogen compounds, such as sodium chlorid,

fluorspar, cryolite, calcium chlorid, etc.

Under the described conditions, the copper or other metal in contact with the steel 1 may be melted and raised to any suitable temperature, such as the supermolten temperature, or it may, of course, be melted prior to bringing it in contact with the steel and then further'heated, or its heat maintained, during the operation. Under the described conditions since the maximum temperature of the copper will prevail along the line of intended union, and any desired time for solidification may be given, the described difliculties incident to the ordinary casting operation do not occur. The copper layers most remote from the steel maybe caused to solidify first. Where high conduc tivity, either for heat or electricity, is desired, it is a useful expedient at times to keep these outer layers cooled below the melting point as in such event any contamination of the layers beyond those next the steel with dissolved iron cannotoccur. The

presence of iron in copper reduces its heat conductivity out of all proportion to the amount of such iron. The steel may. of

course be preliminary film coated with copby the methods deper or copper iron alloy scribed in Patent 853,716. g

A useful preliminary to the operation is to produce more or less pure iron on the surface of the steel. Iron unites with copper very much more readily than doesrsteel, and at lower temperatures, the resence of the carbon in the steel material y reducing the tendency toward union. In this reliminary treatment, the steel object may, gr instance, be first oxidized and then re-reduced, as by exposing it in a heated condition to an atmosphere of producer gas. In the oxidation, the superficial carbon burns 'out more or less thoroughly and the iron reduced from the oxid is substantially pure. A better way, however, is to first treat the steel by exposure to superheated streaming steam which causes the formation of a thin, closely cohering coating of a ferrosoferric or magnetic oxid on its surface. This coating coheres much better to steel than do ordinary oxid coats and is in molecular contact with the underlying metal. By now heating, the

underlying superficial carbon of the steel reduces this oxid, forming pure iron both from the oxid and also from the underlying layers. With this pure iron, copper readil unites. The heat of molten copper is cient to perform the-oxid-reducing reaction sation of bubbles of liberated oxids of carbon. With a clean steel billet and with-coppercontaining, as it usually does, both dis-- solved oxid and oxygen, instead'of first oxidizing the steel, the oxygen inthe'cofpper may be employed to burn out the super cial carbon .ef the steel and produce the desired pure iron. Azuseful specific way of performing the present invention, assuming that an exteriorly clad tube is required, is to sandblast and pickle a steel tube, which may be of any steel desired and made in any desired manner as by lap welding, Mann'esmann draw- 1 and the desired union with the copper is attained. Or the-tube may be cleaned, sandblasted and pickled'to obtain'a true metallic surface and then copper containin oxygen cast or' flowed around itin a suita le mold while interiorly heating until union is effected. Or the cleaned tube may be simply.

interiorly heated in contact with pure copper until such copper is not only melted but ecomes supermolten: After the union is effected, the cladtube may be removed and given a final pass or two to reduce it somewhat in gage andto compact the coating. It may, for example, be cold drawn. Thls working-has the useful eflect of producing an advantageous physical change in the coating metal whichbeing compacted between the workin tool on the one side'and the relatively sti hard metal on the other while held against lateral yielding by the existence of a basal Weld union, assumes throughout its mass a peculiar texture comparable with the surface texture of hard drawn wire.

This much'improves it for. most purposes requiring strength and a,

a weld union, resisting discovery-by cleav- I irtitg tools, such as a cold chisel, or by the e ect of heating and quenching. .The, two metals do not part by the influence of temperatures short of the melting point of the coating metal. And for heat transferring purposes, as in'boile'r tubes and the like, the presence of the layer of copper whether interior or exterior muchimproves the efli 65' and the point where the .unionof copper and 1 steel is completed maybe told by the cesciency by providing for a lateral spreading and equalizing of heat in a way impossible withv an all-steel article.

Where it is desirable, as it often is, that.

the metal of the coating shall not be contaminated to any extent by dissolved iron,

' the coating layer may be cold .on the side by steel bands 2. At its bottom, it is proof the steel body in amount sufficient to. mainta n the proximate layer of copper removed from the iron or steel. For example, in producing a tube clad with an outer copper layer, the copper may be cast into contact with the interiorly heated tube in a mold having cooling means in the wall. By properly controlling the cooling, the outer layers of the copper coating may be solidified and kept solidified while the layers next the iron or steel are left liquid and form the union with the ferrous metal. Or a sleeve of copper surrounding the iron or steel may be melted in the layers in contact vided with arecess wherein seats an annular steel body 4, In the chamber between the annular steel body and the mold is a body of copper 5. Covering this body may be a cover 6. Flame producing means 7 are adapted to .direct a .brush flame of oil, gas or the like within the annular steel body. Above the flame chamber is hood 8 for removal of gas.

The use of the apparatus shown is obvious from the foregoing. Steel body 4 having been seated within the mold Qliquid or solid copper .5 is filled in the spaces between. Heat isnow applied "from 7 until union is efiected between'the copper and steel.

What I claim is':

1. The process of making copper clad steel which comprises contacting a body of steel with a body of copper on one side and applying heat to the other side of the steel body in amount'suflicient to maintain the proximate layer of copper molten until a union is effected the application of heat being in such manner as to maintain such proximate layer of copper at a higher temperature than the rest of the copper.-

2. The process. of making copper cladsteel which-comprises contacting a tubular body ofsteel with a body of copper onone slde and applying heat to the-other side steel which comprises oxidizing one side of a body of steel, contacting the oxidized side with a body of copper and applying heat to the other side of the steel body till a union is effected.

4:. The process of making copper clad steel which comprises oxidizing one side of a tubular body of steel, contacting the oxidized side with a body of copper and applying heat to the other side of the steel body till a union is effected.

5. The process of making copper clad steel which comprises oxidizing one side of a body of steel by heating in an atmosphere of steam, contacting the oxidized side with a body of copper and applying heat to the other side of the steel body till a union is efi'ected. v I 6. The process of making copper clad steel which comprises oxidizing one side of a tubular body of steel by heating in an atmosphere of steam, contacting the oxidized side with a body of copper and applying heat to the other side of the steel body till a union is effected. a

7. The process of making copper clad steel which comprises contacting a body of steel with a solid body of copper on one side, and heating the other side of the steel body till the copper is melted and a union effected.

8. The process of making copper clad v steel which comprises contacting a tubular body of steel with a body of copper on one side, applying heat to the other side of the steel body in such amount and manner as to maintain the proximate layer of copper at Ya higher temperature than the rest of the copper and maintaining such application of .heat until a weld union is effected between the copper and the steel. 9. The process of making copper clad steel whichcomprises oxidizing one side of a body of steel, contacting the oxidized side with a body of copper and applying heat to the other side of the steel body till the copper is melted and a union efi'ected.

10. The process of making copper clad steel whichcomprises oxidizing one side of a tubular body of steel, contacting the oxidized-side with a body of copper and applyingh eat to the other side of the steel body .till the copper is melted and a union efvfected.

11. The process of making copper clad steel which comprises oxidizing one side of abody of steel by heating in an atmosphere otsteam, contacting the oxidized side with a body of copper and applying heat to the heat to the other side of the steel body till other side of the steel body till the copper the copper is melted and a union effected. 10 is melted and a union efiected. In testimony whereof, I aflix my signature 12. The process of making copper clad in the presence of witnesses.

' steel which comprises oxidizing one side of; VVILLIAM MARSHALL PAGE.

a tubular body of steel by heating in an at- W'itnesses: mosphere of steam, contacting the oxidized P. M. WEIs, side With a body of copper and applying JOHN B. PATTON. 

